1. Field of the Invention
The present invention relates to a gas contamination measuring apparatus, more particularly, to an apparatus which is installed at the front side of the light path of an ultravioletemitting laser apparatus to detect the presence of environmental contamination.
2. Description of the Related Art
Recently, the group of high output lasers (excimer lasers) has been used in generating light in the UV range of the spectrum (for example, XeF laser at 353 nm, XeCl laser at 308 nm, KrF laser at 248 nm, ArF laser at 193 nm, F.sub.2 laser at 157 nm, XeB.sub.2, etc.).
The lasers are stimulated or pumped by the action of discharge, excitation by collision of electrons, or vibration of a resonator.
These lasers, however, may be used as simply movable wave amplifiers without a resonator. If an ultrashort pulse of light having a wavelength within the amplification range of the excimer laser used is provided and its action condition is set properly, it is possible to obtain an ultrashort pulse with very high sensitivity.
Conventionally, the laser beam produced from laser apparatus which generates ultraviolet rays or deep ultraviolet rays has powerful energy of which the mean power is several hundred thousand watts and the peak power produced is up to 10.sup.5 .about. 10.sup.10 watts. Accordingly, if dirt is present in the laser path, the dirt is resolved and changed into reaction products which are deposited onto the optical elements, thereby resulting in problems that the strength of laser is decreased and the functional element in the laser apparatus must be changed.